Gas treatment and apparatus therefor



March 4, 1952 G, F. RUSSELL, JR

GAS TREATMENT AND APPARATUS THEREF'OR lFiled Feb. 15, 194e Patented Mar.4, 1952 GAS TREATMENT AND APPARATU THEREFOR George Franklin Russell,Jr., Baton Rouge, La.,` `assgnor to Aluminum Company of America,Pittsburgh, Pa., a corporation of Pennsylvania Application `February 15,1946, Serial No. 647,750

5 Claims. 1

This invention relates to improved methods for recovering from wellsgaseous hydrocarbon fluids, particularly natural gas, and to improvedsystems for receiving, handling and treating such gases.

Among the problems encountered in the re covery of gaseous hydrocarbonfluids, such as natural gas, from the earth and placing the gas inusable form are the diiculties encountered in protecting from corrosionthe recovery apparatus and particularly thecasing elements of the welland the pipe or tube through which the gas is withdrawn from the well.Another problem encountered is the provision of eflicient `means bywhich the gas maybe "driedf i. e., stripped of its moisture content.Since the corrosion difculties just referred -to are inlarge part causedbythe moisture carried by the gas, these problems are, in a sense,related. Natural gas as it is recovered from the earth usuallyfbearsconsiderable moisture. As the gas moves upwardly from the relativelywarm subterranean levels to the relatively cool levels, this moisturecondenses upon the well casing and the gas carrying tube disposedtherein and causes thecorrosion `herein referred to. When'the naturalgas also bears acidic components the corrosion effect may beconsiderably increased.

An important object of this invention is `the provision of methods bywhich such corrosion may be minimized or substantially eliminated.Another object of the invention is to provide an efficient gas handlingand treating system by which the rst mentioned object may be realised.

A further object of the invention is provision `of an improved gashandling and drying system having new and novel features including anefficient combination of means for drying the gas by use of a sorbentand means for reactivating said sorbent. Yet `another object is theprovision of an efficient gas handling system in which the pressure ofthe recovered gas is utilized to effect certain operations in saidsystem. These and further objects of the invention, as well as theadvantages and benefits obtainable bythe practice thereof, will moreparticularly appear from the following description.. The drawing, whichwill be referred to insa-id description, illustrates in diagrammaticform a preferred system ernbodying the principles of this invention.

Referring to the drawing, the well illustrated therein consists of aconventional casing lll, which, extends into the producing formation Il.Casing head (l2 is likewise conventional and through it passes the`tubel I3 which collects the gas .and delivers the same to the gashandling and treating system. It is on the surfaces of the tube, thecasing and the` casing head that much of the corrosion difficultiesoccur. As the moisture-bearing gas passes .from the earth to therelatively cool conditions existing abovethe surface of the earth,moisture .condenses on ,the casing and particularly on the inner surfaceof tube t3. The resultant corrosion `limits the useful life of `tube I3and, often, the lifeof casing I0. The method of this. invention designedt0 minimize or eliminate these corrosion effects consists in mixing withthe gas at the bottom` of the casing and prior to its travel to the`surface of the ground, ofsuch amounts ,of `a dry gas `as are calculated`to reduce the moisture content ofthe mixture thus formed below thepoint ,at

which substantial condensation will occur in the gas carrying tube, i..ebelow the dew point of the gas-dry gas mixture. The amount of drygasnecessary to this purpose will, of course, depend upon the originalmoisture content of the gas .to be recovered and thetemperatureconditions pre,- vailing during passage of that gas from the.earth tothe surface ,or to the next step of the gas handling operati-ons, but isreadily.. calculated when these conditions, which .are easilyascertainable, are known. The naturev of the .dry gas is-not importantto this invention, in so far as concernsthe reduction of the dew `pointof ,the gasbeing recovered. However, it is preferable to use as the drygas aportion of the recovered gas which has been previously dried and,in any event, the dry gas should Abe substantially .nonreactive with thematerialsfrom which the .gas handling apparatus is formed and should.preferably be a type which does not form explosive mixtures with therecovered gas. The manner in which the mixture between drygas and themoisture-bearing gas is `formed may vary with the choice of theoperator, butconveniently the dry gas is merely forced Aunder pressure`.downf wardly to the `bottom of the casing. Forthis purpose the drygas-may Ibe furnished through the casing headby, a pipe or tube,l suchas tube lli shown in the drawing. AThe gas handling and treatingapparatus which is particularly useful in the practice of theaforestated method ofthis invention is shown 'inthe drawing Aand-willnow be specifically described. The general purpose rof the system is toprepare anatural' gasforH-de livery toa consumer orto storageffor lateruse. A `specific purpose is to deliver to the' ywell a quantity of drygas for' the purpose 'above stated. The general function "of f the 1system isfto dry 1and I purify the gas, the principal drying means beinga sorbent, such as adsorbent alumina, silica gel, or other known sorbentwhich is capable of being revived or reactivated. The adsorbentcorn-mercially availabe as Activated Alumina is particularly suitable.The preparation of such material is described in U. S. Patents 1,868,869and 2,015,543. To these ends the specc system shown includes threeidentifiable but mutually interdependent circuits, viz., a receiving andtreating circuit, a sorbent reactivating circuit, and a feed circuitdesigned to furnish dry gas under pressure to the well casing. Each ofthese circuits will now be described.

The receiving and treating circuit The circuit is fed by gas issuingfrom the well through tube I3. The gas passes through heat exchanger I5,tube I6 and separator I'I. From separator I'I the bulk of the gas movesthrough tube I8 and thence through one of the drying towers I9 or 20 fortreatment with a sorbent. From the tower the gas flow continues throughpipe 2I, the bulk of the gas then passing through expansion motor 22,pipe 23, heat exchanger I5, and then through pipe 24 to the consumer orto storage. It will be noted that during the time the natural gas isbeing puriiied and dried, it is under substantially the pressure atwhich it entered the system, subject, of course, to changes intemperature and incidental losses. However, when the gas iiow reachesexpansion motor 22, the gas is expanded to cool it and the energy thusreleased is used to operate motor 22 to drive a compressor 34 forpurposes later described. To this end the motor is any conventionaldevice adapted to expand the gas and permit the expansion to operate apiston or like driving part. As the unpuriiied natural gas iiows throughheat exchanger I5, its temperature is reduced by the cooling action ofthe dried and puried gas which, having been expanded at expansion motor22, passes through tube 23 to and through said heat exchanger. Theunpuried and undried natural gas, now partially cooled by the action ofthe heat exchanger I5 just described, next is subjected to the action ofseparator II. Here the condensate which may have resulted from thecooling action is collected and discharged through pipe 40 to a suitableplace, while the gas passes to the drying tower. While, for convenienceof illustration, only two drying towers are shown, it will be realizedthat any number of such towers may be used, the principle being that atany given time one or more of said towers are available for use, whileone or more towers previously used are being reconditioned ior futureuse. Thus, in the device shown, by manipulation of valves 4I and 42, oneof the towers I9 and 20 may be placed in circuit with separator I'I andexpansion motor 22, while the other tower is excluded from said circuit.For the purposes of drying, the tower contains a sorbent of the typeabove described.

The sorbent reactiuating or reconditioning circuit The purpose of thiscircuit is to divert from the receiving and treating circuit a portionof gas which is then heated to a proper temperature and passes throughthe inactive tower to recondition or reactivate the sorbent heldtherein. Thereafter this gas is returned to the receiving and treatingcircuit of the system. Referring now to' that point in the receiving andtreating circuit where the gas leaves separator Il, a

portion of the gas is diverted through tube 25 to heater 21, the amountdiverted being controlled by valve 26. Heater 2'I is conventional. Itis, of course, desirable, all other conditions being equal, to use as areactivating gas a gas which has at least been partially dried. It isfor that reason that it is preferred to take the reactivating gas fromthe circuit after the gas has passed through separator I'I. Fuel for theheating is delivered thereto from any convenient source (including apoint in the system) by pipe 4l. The temperature of the heater isregulated to deliver therefrom gas at reconditioning or reactivatingtemperature. These temperatures are known and depend upon the sorbentused in the drying tower. For instance, when adsorbent alumina is thesorbent used, the temperature of the gas as it leaves the heater shouldpreferably be in the range of 350 to 600 degrees Fahrenheit. On leavingthe heater, the diverted and now heated gas passes through tube 28 to adrying tower and thence from the tower through tube 29, then throughheat exchanger 30, where the gas is somewhat cooler, then throughseparator SI and tube 32, which directs the gas iiow into the dryingtower then being used in the receiving and treating circuit, at whichpoint the diverted gas rejoins the receiving and treating circuit andbecomes a part thereof. The function of heat exchanger 30 will be laterdescribed. The function of separator 3| is to separate condensate, whichcondensate passes through pipe 48 to a suitable place. It Will be notedthat by manipulation of valves 43 and 44 this sorbent reactivationcircuit is diverted through and includes the drying tower which is not,at that moment, a portion of the receiving and treating circuit, whilethe gas diverted to the sorbent reactivation circuit is finally returnedto the redried in the other drying tower.

The feed circuit which delivers dry gas to the well circuit This circuitbegins at a point in the receiving and treating circuit between thedrying tower and expansion motor 22 and terminates when it delivers thedried gas to the well casing for mixture there with the moisture-bearingnatural gas being recovered. Thereafter the dried gas is returned to thereceiving and treating circuit in said mixture subject, of course, toincidental losses which may occur at the bottom of the well casing. Thedried gas enters this circuit through tube 33, the amount so divertedfrom the principal circuit being controlled by valve 46. The gas thenpasses through compressor 34, where it is compressed to a pressuredesirable or necessary for its subsequent entry into the well. From thecompressor 34 the compressed dry gas passes through tube 35 to andthrough heat exchanger 3U and thence through pipe I4 to the Well. Inheat exchanger 30 the temperature of the dried gas is raised by the heatloss of the heated gas from the reactivation circuit which, as abovedescribed, likewise passes through said exchanger. The heating of thedry gas prior to the time it enters the well is desirable as additionalassurance that corrosion condensate will not form on the walls of thewell elements. The amount of gas diverted to this circuit will depend,as above described, on the temperature conditions existing in the welland at the surface and the moisture content of the natural gas beingrecovered.

From the above description of the illustrated, and preferred, form ofgas handling system, it will bezamiarentthat,V viewedtas af, who1e; thesystemA circuit including atleasttoneoi` saidtowers and` in whichnaturalgasfdelivered-from a. gas well is rdried=` at substantially `thepressure ofi delivery,

a` reactivating` circuitfrcceiving undried gas from` the 'dryingcircuit, including atleast oneof .said

towers and also including means for heating the.

undriedgas prior toits entry into said tower, this reactivatirrgcircuitA terminating; in: thedrying circuit at a point prior toinaldrying,-v anda feed circuit i adapted to f divert'. a f portion of the`dried gas from the drying circuit to the Well, this feed circuitincluding` means for compressing` the gas operable jby` expansion lof`the driedz gas I.traveling through the=drying circuit and alsoincludingheating rmeans f or raising the temperature of the compressedgas;- saidxl'ieatingbeingc electedby transfer of heat from-the gastraveling` in the:

reactivation circuit.

Thus far the. above describedsystem has been considered asan improvedmeansi'or` carrying out the Apreviously described corrosion preventing`methods of the invention.. It will` betnotedthat even in thisform `thereactivation circuit may be eliminatedwithout destroying the systemsusefulness as applied to such methods. For instance, if the drying`agent usedv in the dryingtower is of. a type which cannot be revivedor` reactivated after useor inthe reactivationV force or fluid` is bestfurnished separately ofthe system, then the system described may bemodified by removing the reactivation circuit or by shutting valves 2.?,ill` andli, in whichcaseif heating of. thecompressed gas in the dry gasfeedsystem is desirable, i

this heating may be. accomplished by separate means or, Where the gas.issuing. through: tube I3 is quitewarm, by heat exchange withdryingcircuit.

Likewise the. above described system may be. used solely asadryingsystemin casestwhere no,

feed of dry gasto, the wellisdesirable or neces-i- -sary or where drygas `is fed; to the well fromanother source. Inthiscase the feed circuitmay` be eliminated or,. equivalently,.valve.46 may be closed. In such.case, if. cooling of the reactivating gas Ais desired, the cooling4 maybe effected by other means or by heat exchange with a portion of thedried gas after expansion. Likewise the expansion motor maybeeliminated, and` replaced.

by a conventional expansion chamber, or the motor may be retainedand theexpansion energy translated thereby into useful work of any kind.

In a further modification of the system, whether used solely as a dryingsystem or also as a means of furnishing dry gas to the well, the returnof the gas in the reactivation circuit to the dryingoperationmay beeliminated. This case presupposes either that mixture of thereactivationgas directly with the dried gas. will not unduly raisemoisture content. ofy the mixture or thatthe reactivation gas isof. suchsmall quantity thatwastage thereof is of noimportance. In the rst casethe valve i5 may be closed and the gasA issuing from separator 3ldelivered through a by-pass tube 36 to tube24, or tube 32 may bedirectly connected to the consumer line and its connections with thedrying towers eliminated. In the second case the reactivation gas couldbe delivered to the atmosphere from separator 3! or delivered and burnedat some convenient point.

Another modiiication of my system now to be explained is particularlyadapted to carry out a modified method of corrosion prevention in whichlack of moisture in the gas.

with the natural gas inthe volume desired,` the total mixture will be atsuchv temperature that no substantial condensation will occurduringpas-` sageof the mixture from theearth to thehandling system.Thus, in this method thefeed gas is preconditioned with respect totemperature rather than with respect to moisture content, the resultbeing the same. The system above described mayfconveniently be used toachieve this result by bleeding a portion of the undried` heated gasfrom the heater 2.1 directly to tube I4, as through tube 50, in whichcase the valves Miwould be closed or the dry feed circuit to the well,apart from tube I4, entirely eliminated.

These and similar modifications will suggest themselves to those skilledin the art, in the practice of my improved methods, as will such detailsas the fact that the casing may be utilized as the carrier for theup-coming gas in the well,

while an auxiliary tube may be used to transmit conditioned incoming gasto the lower regions of the well, and all such modications are within.the purview of this invention, except as limited by the terms of theappended claims.

The advantages of the gas handling systems herein described aremanifold. The preferred form described, comprising the threeinterdependent circuits, eiiiciently utilizes the energy `inherent inthe pressure of the gas issuing from the well and likewise cuts heatlosses to a minimum, while at the same time conditioning the gas to befed to the well. Considered as a drying system, and without reference tothe i conditioning of gas for well use, my system allows well, saidsystem comprising, in combination, a i

receiving and treating circuit comprising, in recited sequence, meansfor receiving the gaseous fluid from said well, means for holdingV amass of gas drying sorbent in the. path of.flow of said gaseous fluid,and means for expanding the dried` gaseous fluid prior to deliverythereof from the circuit, said circuit being adapted to maintain thegaseous iiuid. at the approximate pressure of its receipt, subject tochanges in temperatureand the herein recited diversions of fluid from.said circuit, until said gaseous fluid enters said expansion means, asorbent reactivating circuit including, in recited` sequence, means fordiverting thereto` a. portion of theY gaseousfluid flowing in. said.receiving and treating circuit, means. for heating the divertedgaseousnuid, means for holding a mass of sorbent in. the path of flow ofthe thus heated gaseous fluid and means for returning said gaseous flowto said receiving and holding circuit, and a feed circuit for feedingdried gaseous :duid from said receiving and holding circuit into saidwell, said feed circuit including, in recited sequence, means fordiverting thereto a portion of said dried gaseous fluid, means forcompressing the diverted dried gas and means for delivering saidcompressed gas into said well, said compressing means being operable bythe expansion means of the said receiving and treating circuit, and aheat exchanging means disposed in said system to transfer a portion ofthe heat content of the gaseous fluid flowing through said returningmeans of the said reactivation circuit to the gaseous fluid flowingthrough said delivery means of the said feed circuit.

2. A system for receiving, handling and treating moisture bearinggaseous hydrocarbon uid issuing, under relatively high pressure, from aWell, said system comprising, in combination, a receiving and treatingcircuit comprising, in recited sequence, means for receiving the gaseousfluid from said well, means for holding a mass of gas drying sorbent inthe path of flow of said gaseous uid, and means for expanding the driedgaseous fluid prior to delivery thereof from the circuit, said circuitbeing adapted to maintain the gaseous fluid at the approximate pressureof its receipt, subject to changes in temperature and the herein reciteddiversions of fluid from said circuit, until said gaseous fluid enterssaid expansion means, a sorbent reactivating circuit including, inrecited sequence, means for diverting thereto a portion of the gaseousuid nowing in said receiving and treating circuit, means for heating thediverted gaseous fluid, means for holding a mass of sorbent in the pathof now of the thus heated gaseous fluid and means for returning saidgaseous ilow to said receiving and holding circuit, and a feed circuitfor feeding dried gaseous uid from said receiving and holding circuitinto said well, said feed circuit including, in recited sequence, meansfor diverting thereto a portion of said dried gaseous fluid, means forcompressing the diverted dried gas and means for delivering saidcompressed gas into said well, said compressing means being operable bythe expansion means of the said receiving and treating circuit, a heatexchanging means disposed in said system to transfer heat from gaseousfluid owing through the returning means of said reactivation circuit tgaseous fluid flowing through the delivery means of said feed circuitand another heat exchanging means disposed in said system to transferheat from gaseous fluid flowing through the receiving means of thereceiving and treating circuit to gaseous fluid flowing from theexpansion means of the same circuit. Y

3. A system for receiving, handling and treating moisture bearinggaseous hydrocarbon fluid issuing, under relatively high pressure, froma Well, said system comprising, in combination, a receiving and treatingcircuit comprising, in recited sequence, means for receiving the gaseousfluid from said well, means for holding a mass of gas drying sorbent inthe path of flow of said gaseous fluid, and means for expanding thedried gaseous fluid prior to delivery thereof from the circuit, saidcircuit being adapted to maintain the gaseous fluid at the approximatepressure of its receipt, subject to changes in temperature and theherein recited diversions of uid from said 8 circuit, until said gaseousfluid enters said expansion means, and a feed circuit for feeding driedgaseous fluid frbm said receiving and holding circuit into said well,said feed circuit including, in recited sequence, means for divertingthereto a portion of said dried gaseous fluid, said means beingpositioned to divert said portion prior to its entry into the expansionmeans i of the receiving and treating circuit, means for compressing thediverted dried gas and means for delivering said compressed gas intosaid well, said compressing means being operable bv the expansion meansof the said receiving and treating circuit.

4. A system for receiving, handling and treatine.r moisture bearinggaseous hydrocarbon fluid issuing, under relatively high pressure, froma well, said system comprising, in combination. a receiving and treatingcircuit, including gas drying sorbent and means for transmitting saidgas from the well through a portion of said sorbent, a sorbentreactivating circuit, including a heater and means for transmitting aportion of the gas from said well through said heater and throughanother portion of said sorbent to reactivate the same, and thence tosaid receiving and` treating circuit, a feed circuit for feeding aportion of the dried gaseous iiuid from said, receiving and treatingcircuit into said well, and a heat exchanger disposed in said system totransfer heat from the heated gas flowing in the reactivating circuit tothe gas flowing to the well through said feed circuit.

5. A system for receiving, handling and treating moisture bearinggaseous hydrocarbon fluid issuing, under relatively high pressure, froma well, said system comprising, in combination, a receiving and treatingcircuit, including gas drying sorbent and means for transmitting saidgas from the well through a portion of said sorbent, a sorbentreactivating circuit, including a heater and means for transmitting aportion of the gas from said well through said heater and throughanother portion of said sorbent to reactivate the same, and thence tosaid receiving and treating circuit, a feed circuit for feeding aportion of the dried gaseous fluid from said receiving and treatingcircuit into said well, and a heat exchanger disposed in said system totransfer heat from undried gas flowing from said well to dried gasdischarging from said receiving and treating circuit.

GEORGE FRANKLIN RUSSELL, J r..

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 956,058 Elten Apr. 26, 19101,763,984 Husted July 1, 1930 1,978,655 Straight Oct. 30, 1934 2,160,831Colby et al June 6, 1939 2,204,042 Legatiski June 11, 1940 2,309,075Hill Jan. 19, 1943 2,323,524 Downs, Jr. July 6, 1943 2,342,165 PlummerFeb. 22, 1944V 2,355,167 Keith Aug. 8, 1944,

